<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category  Zend
 * @package   Zend_TimeSync
 * @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd     New BSD License
 * @version   $Id: Sntp.php 16209 2009-06-21 19:20:34Z thomas $
 */

/**
 * Zend_TimeSync_Protocol
 */
require_once 'Zend/TimeSync/Protocol.php';

/**
 * SNTP Protocol handling class
 *
 * @category  Zend
 * @package   Zend_TimeSync
 * @copyright Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_TimeSync_Sntp extends Zend_TimeSync_Protocol
{
	/**
	 * Port number for this timeserver
	 *
	 * @var integer
	 */
	protected $_port = 37;

	/**
	 * Socket delay
	 *
	 * @var integer
	 */
	private $_delay;

	/**
	 * Class constructor, sets the timeserver and port number
	 *
	 * @param string  $timeserver Timeserver to connect to
	 * @param integer $port       Port of the timeserver when it differs from the default port
	 */
	public function __construct($timeserver, $port)
	{
		$this->_timeserver = 'udp://' . $timeserver;
		if ($port !== null) {
			$this->_port = $port;
		}
	}

	/**
	 * Prepares the data that will be send to the timeserver
	 *
	 * @return array
	 */
	protected function _prepare()
	{
		return "\n";
	}

	/**
	 * Reads the data returned from the timeserver
	 *
	 * @return string
	 */
	protected function _read()
	{
		$result       = fread($this->_socket, 49);
		$this->_delay = (($this->_delay - time()) / 2);

		return $result;
	}

	/**
	 * Writes data to to the timeserver
	 *
	 * @param  string $data Data to write to the timeserver
	 * @return void
	 */
	protected function _write($data)
	{
		$this->_connect();
		$this->_delay = time();
		fputs($this->_socket, $data);
	}

	/**
	 * Extracts the data returned from the timeserver
	 *
	 * @param  string $result Data to extract
	 * @return integer
	 */
	protected function _extract($result)
	{
		$dec   = hexdec('7fffffff');
		$time  = abs(($dec - hexdec(bin2hex($result))) - $dec);
		$time -= 2208988800;
		// Socket delay
		$time -= $this->_delay;

		$this->_info['offset'] = $this->_delay;

		return $time;
	}
}
